Telemetry to Count Top Level & Transitive source mappings automatically created

[donnie-msft]

Bug

Fixes: https://github.com/NuGet/Client.Engineering/issues/2450
Fixes: NuGet/Home#12839

Regression? Last working version:

Description

• Telemetry will now have 2 integer properties for counts of added top-level and transitive package source mappings.
• Top-level values can either be 0 or 1 in the current implementation (may become >1 in future iterations)
• In scenarios when automatic mapping is not possible, the properties are not created (will be missing from telemetry).
• See description of Issue for telemetry samples
• Implements more of Assessment: https://github.com/NuGet/Client.Engineering/blob/main/designs/telemetry/assessment-source-mapping.md
• Secondarily, some refactoring is done in the utility class to return the counts
• Thirdly, the utility class implementation has changed
  • Determine in ConfigureNewPackageSourceMapping whether the top-level is already mapped, to avoid telemetry emitting count:1 for top-level when it's already mapped.
  • Remove an unnecessary array.

PR Checklist

• PR has a meaningful title

• PR has a linked issue.

• Described changes

• Tests

  • Automated tests added
  • OR
  • Test exception
  • OR
  • N/A

• Documentation

  • Documentation PR or issue filled
  • OR
  • N/A

[donnie-msft]

The vision I have here is when multiple top-levels can be passed in and mapped, the count will become:

Suggested change

	countCreatedTopLevelSourceMappings = 1;
	countCreatedTopLevelSourceMappings++;

[aortiz-msft]

The problem with this calculation is that, if there's a bug in the logic in this function, telemetry would not help us understand what the bug is. Instead, I suggest incrementing the counter after line 61 (within the else if) and reporting that.